Download How Germs Spread - Oklahoma 4-H

Objective
Students will conduct scientific experiments to learn how germs are spread.
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How Germs Spread
Background
I. HOW GERMS SPREAD
The most common way for infectious disease to spread is through the
direct transfer of bacteria, viruses or other germs from one person to another.
This can occur when an individual with the bacterium or virus touches, coughs
on or kisses someone who isn’t infected. These germs can also spread through
the exchange of body fluids from sexual contact or a blood transfusion.
Animals carry many germs. Being bitten or scratched by an infected
animal can make you sick. You might also become infected by scooping your
cat’s litter box or by cleaning mouse droppings in your house or garage. The best
way to prevent this is to wash your hands often.
Disease-causing organisms can also be passed along by indirect contact.
Many germs can linger on an inanimate object, such as a tabletop, doorknob or
faucet handle. When you touch the same doorknob grasped by someone ill with
the flu or a cold, for example, you can pick up the germs he or she left behind. If
you then touch your eyes, mouth or nose before washing your hands, you may
become infected.
When you cough or sneeze, you expel droplets into the air around you.
When you’re sick with a cold or the flu—or any number of other illnesses—
these droplets contain the germ that caused your illness. Crowded, indoor
environments may promote the chances of droplet transmission.
Some disease-causing germs travel through the air in particles
considerably smaller than droplets. These tiny particles remain suspended in the
air for extended periods of time and can travel in air currents. If you breathe in
an airborne virus, bacterium or other germ, you may become infected and show
signs and symptoms of the disease. Tuberculosis and SarS are two infectious
diseases usually spread through the air, in both particle and droplet forms.
Some germs rely on insects—such as mosquitoes, fleas, lice or ticks—
to move from host to host. These carriers are known as vectors. Mosquitoes
can carry the malaria parasite or West Nile virus, and deer ticks may carry the
bacterium that causes Lyme disease.
Another way disease-causing germs can infect you is through food and
water. Escherichia coli (E. coli) is a bacterium present in certain foods, such as
undercooked hamburger or unwashed fruits or vegetables. When you eat foods
contaminated with E. coli, chances are you’ll experience an illness, also referred
to as food poisoning.
II. WHAT IS A PANDEMIC?
A pandemic is an epidemic (an outbreak of an infectious disease) that
spreads across a large region (for example a continent), or even worldwide.
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Oklahoma Academic
Standards
GRADE 5
Science—5.PS.1.4;
5.LS.2.1,2
COMMON CORE
Math Practice—
MP.1,2,4,6,7
Math Content—5.MD.B.2
English Language
Arts—5.RI.1,7,9,10;
5.W.2,4,5,6,7,8,9,10
GRADE 6
Science—MS.LS1.1,3, 2.2,4
COMMON CORE
Math Practice—
MP.1,2,4,6,7
Math Content—6.
SP.A1,2,B4
English Language
Arts—6.RI.1,7,9,10;
6.W.2,4,5,6,7,8,9,10
GRADE 7
Science—MS.PS1.2;
MS.LS4.4
COMMON CORE
Math Practice—
MP.1,2,4,6,7
Math Content—7.SP.A.1,2,
B.3,4
English Language
Arts—7.RI.1,9,10;
7.W.2,4,5,6,7,8,9,10
Materials
phenolphthalein
bleach
water
clear plastic cups
500 ml beaker
25 ml graduated cylinder
What is a Germ?
The term “germ” refers to any
microorganism, especially
those microorganisms that
cause disease. Included in this
category are certain viruses,
bacteria, and fungi.
Viruses are simple organisms
that are so tiny they can only
be seen with a special, very
powerful microscope called an
“electron microscope.” They
are so simple that they are
technically not even considered
alive, since they are not able to
metabolize, grow, or reproduce
on their own. Instead they
must take over a host cell that
provides these functions.
Bacteria are much larger in
size and can live anywhere.
There are bacteria in the soil,
at the depths of the ocean, on
the surfaces of teeth, and in the
digestive tracts of humans and
animals. Most bacteria are not
pathogenic (disease-causing).
In fact, many bacteria are very
helpful to us. There are species
that decompose trash, clean
up oil spills, and even produce
medicines.
Fungi are larger, plant-like
organisms that lack chlorophyll
(the substance that makes plants
green and converts sunlight
into energy). Since fungi do not
have chlorophyll to make food,
they have to absorb food from
whatever they are growing on.
Fungi can be very helpful—
making bread rise, decomposing
trash—but they can also be
harmful if they steal nutrients
from another living organism.
According to the World Health Organization, a pandemic can start when
three conditions have been met:
1. A disease new to the population emerges.
2. The agent infects humans, causing serious illness.
3. The agent spreads easily and sustainably among humans.
A disease or condition is not a pandemic merely because it is widespread or
kills many people; it must also be infectious.
One infectious disease that has begun to worry medical professional
is the H5N1 avian influenza virus, commonly known as avian flu. The avian
flu virus is found in wild birds, especially among waterfowl (ducks, geese,
gulls). It is highly contagious and can infect domesticated birds, such as
chicken, ducks, and turkeys. There have been no cases of avian flu reported
in wild or domesticated birds in the US. The US Fish & Wildlife Service has
an ongoing surveillance program to test wild birds for H5N1 virus.
Human infection from bird flu is rare but can happen when contact is
made with the cages, equipment, water, or feed. Approximately 160 people
have contracted avian flu worldwide, but there have been no reported cases
in the United States.
Once an animal is sick, no one wants the disease to spread. That
is where biosecurity comes into play. Biosecurity refers to management
practices that reduce the chances infectious diseases will be carried onto a
farm by animals or people.
The US Department of Agriculture (USDA) has safeguards in place
to protect against the introduction of the avian flu and other diseases into
the United States. All live birds imported into the US are quarantined and
tested. Pet birds returning to the US from other countries (except Canada)
also are tested and quarantined at a USDA facility.
Individual poultry producers in the US use these five biosecurity
precautions:
1. Quarantine all new animals for at least 30 days.
2. Properly vaccinate all animals.
3. Wash hands before and after dealing with livestock and wash boots and
clothing after visiting another farm and after dealing with sick animals.
4. Contact proper authorities if an animal is sick or acting oddly or if a
suspicious person has been around.
5. Limit all contact of animals with other animals (wild and domesticated)
and with people from farms where proper hygiene is not practiced.
The USDA works closely with international organizations like the
World Organization for Animal Health (OIE), the United Nations Food and
Agriculture Organization (FAO), and World Health Organization (WHO)
to assist avian flu-affected countries with disease prevention, management,
and eradication activities.By helping these countries prepare for, manage, or
eradicate avian flu outbreaks,
the USDA helps control the spread of the virus.
Background sources: US Department of Agriculture, Oklahoma State Department of
Health, Communicable Disease Division; Nemours Foundation, Kids Health
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Science
1. Read and discuss the first section of the background, “How Germs
Spread.”
—As you read, students will list the way germs can spread.
2. Conduct the following experiment to demonstrate how germs spread.
—Prepare a mixture of 50 ml water and 50 ml bleach. Mark this cup
on the bottom to distinguish it from the other cups, and set it aside.
This will be the teacher’s cup. CAUTION: Great care should be taken
when handling bleach. This is a strong base and can cause irritation.
—Give each student a clear plastic cup.
—Each student will fill his/her cup with 100 ml of water. Instruct
students to not drink from the cups.
—Tell students an infected bird has entered the classroom, and one
unknown person in the class will represent the infected bird.
—Students will hypothesize as to whether the infected bird will affect
other birds and, if so, to what extent.
—Students will spend the next 5-10 minutes mingling and sharing
water by pouring small amounts into each others’ cups, being careful
not to overfill the cups.
—The teacher will use the cup prepared ahead of time to participate in
the mingling without letting students know of the bleach addition.
—After 5-10 minutes stop and ask these questions:
Did you drink after each other?
Did you walk in the contaminated “droppings” of another?
Were you in the same area as other birds (students)?
Do you think you shared any germs?
—Put 5ml (approximately one eye dropper full) of phenolphthalein
into each student’s cup.
—Students will observe what happens: If the water turns pink, a germ
(represented by the bleach) was shared.
—Discuss:
• Was your hypothesis correct? Did the infected bird infect other
birds? To what extent?
• Can germs be easily and unknowingly shared?
• How did the contamination occur?
—Reveal to students that the teacher was the “host bird,” and explain
that phenolphthalein is an indicator for bleach and turns pink when it
comes into contact with bleach.
Refer students to their previous list from the background and ask:
• “How does this activity simulate the transfer of germs?”
• “Which kind of transfer does this activity represent?”
Math
1. Evaluate the number of infections spread to other birds (from the
previous activity).
—Use tally marks on the chalkboard to record the number of cups with
pink water.
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Vocabulary
bacteria—a group of singlecelled microorganisms that live
in soil, water, the bodies of
plants and animals, or matter
obtained from living things and
are important because of their
chemical effects and diseasecausing abilities
biosecurity—management
practices that reduce the chances
infectious diseases will be carried
onto a farm by animals or people.
contagious—capable of being
transmitted by bodily contact with
an infected person or object
fungus—any of a kingdom of
living things (as molds, rusts,
mildews, smuts, and mushrooms)
that lack chlorophyll, are parasitic
or live on dead or decaying
organic matter, and were formerly
considered plants
germ—a microscopic living
thing, especially one that causes
disease
pandemic—an outbreak of
disease occurring over a wide area
and affecting many individuals
pathogen—an agent that
causes disease, especially a
living microorganism such as a
bacterium or fungus
population—a group of
organisms of the same species
populating a given area
quarantine—a strict isolation
imposed to prevent the spread of
disease
virus—any of various simple
submicroscopic parasites of
plants, animals, and bacteria
that often cause disease and that
consist essentially of a core of
RNA or DNA surrounded by a
protein coat. Unable to replicate
without a host cell, viruses are
typically not considered living
organisms.
Ag Career: Microbiologist:
Microbiology is the study of living
organisms that are invisible to the
naked eye, such as bacteria and fungi.
Though not living organisms, viruses
also are studied by microbiologists.
—Students will create a data table to compare the number of
students who shared the germ with the number of students (if any)
who were germ-free.
Language Arts
1. Read and discuss the second part of the background, “What is a
Pandemic?”
—Discuss how an infectious disease like the avian flu might
Though many people tend to group
spread.
them together, there are many different
—How might birds spread disease? (Birds walking in droppings.
types of microbiology. Medical
Birds stung by a mosquito which then stings you.)
microbiology is perhaps the most
—Discuss the differences between viruses, bacteria and fungi. (See
well-known because it deals with the
the sidebar, “What is a Germ?” included with this lesson.)
roles that microbes have in human
—Review “How Reliable Are Your Sources?” in the “Additional
illness. Other types include veterinary
Resources” section of the OAITC website.
microbiology, environmental
—Students will use online or library references to research one of
microbiology, food microbiology and
the common diseases listed below:
pharmaceutical microbiology. All
influenza
measles
these deal with the way microbes or
common
cold
whooping cough
microorganisms affect animals, the
strep throat
athlete’s foot
environment, the food supply and the
parvovirus
distemper
health care industry.
hepatitis
Newcastle disease
Lyme disease
brucellosis
Most microbiologists work in one of
tuberculosis
salmonella
the following fields: hospitals/clinical
blastomycosis
aspergillosis
laboratories, the food industry, the
ringworm
environment, research laboratories
—Students will write reports based on their research. Research
and teaching at community colleges
should determine if the diseases are viral, bacterial or fungal,
or universities. A career as a
if they infect humans, animals or both and which ones can be
microbiologist usually requires an
transferred from animals to humans, and vice versa.
education beyond the high school
—As a class, students will develop a disease comparison chart to
level. Some microbiologists practice
record what they have learned.
with two-year associate degrees in
a scientific field such as chemistry
or biology, but most have at least a
Extra Reading
four-year bachelor’s degree from a
Goldsmith, Connie, Invisible Invaders: Dangerous Infectious
college or university. Typically, these
Diseases, Lerner, 2006.
degrees are given in areas such as
Hooper, Mary, Petals in the Ashes, Bloomsbury Children’s, 2005.
microbiology, chemistry or biology.
Murphy, Jim, An American Plague: the True and Terrifying Story of
Some microbiologists gain master’s
the Yellow Fever Epidemic of 1793, Clarion, 2003.
degrees, which require research and
Reed, Jennifer, The AIDS Epidemic: Disaster & Survival (Deadly
usually lead to teaching positions in
Disasters), Enslow, 2006.
universities or colleges, while others Silverstein, Alvin, Virginia Silverstein, and Laura Silverstein Nunn,
seek doctoral degrees. A doctoral
Disease Update: The Flu and Pneumonia Update, Enslow,
degree, or Ph.D., serves to give a
2006.
microbiologist a great amount of
research experience and extensive
schooling in the field of microbiology.
Source: Bioscience Careers— http://www.
aboutbioscience.org/careers/microbiologist